This invention relates to a constant-voltage circuit, more particularly, to a constant-voltage circuit capable of making an output voltage be stable without an overshoot at a circuit output terminal.
A constant-voltage circuit is for use in obtaining a constant-voltage as an output voltage. A conventional constant-voltage circuit comprises a differential amplifier circuit and an output stage circuit connected to the differential amplifier circuit and will be referred to a first conventional constant-voltage circuit. The output stage circuit may be further connected to an output load circuit at a circuit output terminal. When the differential amplifier circuit is supplied with a reference voltage, the output stage circuit outputs an output voltage as a constant-voltage. As will be described later, an overshoot inevitably occurs at the circuit output terminal in the first conventional constant-voltage circuit. Accordingly, it is difficult to make the output voltage be stable in the first conventional constant-voltage circuit.
In additional, it is known that a constant-voltage circuit is disclosed in Japanese Patent Publication Tokkai Syo 64-29915 (29915/1989) and will be referred to as a second conventional constant-voltage circuit.
Furthermore, it is known that a constant-voltage circuit is disclosed in Japanese Patent Publication Tokkai Hei 1-314319 (314319/1989) and will be referred to as a third conventional constant-voltage circuit.
As will be described later, an overshoot also occurs in each of the second and the third conventional constant-voltage circuits. Accordingly, it is difficult to make the output voltage be stable in each of the second and the third conventional constant-voltage circuits.